Portable electronic apparatus and bag package protective device

ABSTRACT

A portable electronic device in which microswitches ( 12 ) controlled by operation buttons ( 11 ) are mounted on one side of a printed circuit board ( 13 ), and circuit elements accommodated in BGA packages ( 14 ), ( 15 ) and ( 16 ) are soldered on the other side of the printed circuit board. In the portable electronic device, a shield wall ( 22 ) for surrounding the BGA packages ( 14 ), ( 15 ) and ( 16 ) is mounted on the printed circuit board ( 13 ), a first protrusion portion ( 18   b ) for holding down the shield wall ( 22 ) on the printed circuit board ( 13 ) is protruded from a case ( 18 ) of the portable electronic device ( 10 ), and second protrusion portion ( 18   c ) for holding down surfaces of the BGA packages ( 14 ); ( 15 ) and ( 16 ) on the printed circuit board ( 13 ) is protruded from the case ( 18 ) of the portable electronic device ( 10 ). With such a construction, the BGA packages are prevented from being peeled off from the printed circuit board ( 13 ). Further, even when the push buttons are frequently depressed in playing a game, the soldering parts of the BGA packages mounted on the back side of the operation button can be maintained in good conditions.

TECHNICAL FIELD

[0001] The present invention relates to a protecting device forprotecting BGAs (ball grid arrays), which are mounted on a portableelectronic device, such as a portable telephone set (including a simpleportable telephone set), a PDA (personal digital assistant), a portablegame machine and the like. More particularly, the invention relates to aportable electronic device and a BGA package protecting device in whicheven if a pressing force to press down an operation button of theportable electronic device is applied to a printed circuit board ontowhich BGA packages are soldered, a soldering part of the BGA package isnot peeled off.

BACKGROUND ART

[0002]FIG. 8 is a rear view showing a conventional portable telephoneset, and FIG. 9 is a cross sectional view taken on line IX-IX in FIG. 8.An integrated circuit 5 is soldered to a back side of a printed circuitboard 4 a front side of which has microswitches 3 mounted thereon, whichare turned on and off by push buttons 2 of a portable telephone set 1.With an advance of a micro-fabrication technique, the integrated circuit5 of a BGA package type has come to be widely used, recently. Theintegrated circuit 5 of the BGA package type is constructed such that anumber of ball-like terminals are arrayed in a grid fashion on a bottomsurface, and those ball-like terminals are soldered onto correspondingpositions on the printed circuit board 4, respectively. Also for theprinted circuit board 4 which is assembled into the small portableelectronic device, the printed circuit board of the thin type used inrecent years more and more increases its number.

[0003] When a telephone number is entered to the portable telephone set1, the push buttons 2 are successively depressed to turn on themicroswitches 3. At this time, a force of the finger pressing down eachbutton is transmitted to the printed circuit board 4, so that the thinprinted circuit board 4 is somewhat deformed. However, the solderingparts are not peeled off by such a force level as of the operation ofentering the telephone number since the back side of the BGA package 5is soldered onto the printed circuit board 4 over a broad area.

[0004] Recently, the portable telephone set of the type which allows theuser to play a game during a queuing time of the telephone set increasesits number, however. In playing the game, a navigation key for movingthe cursor is in heavy usage. Through frequent and repeated buttondepressions, stress is accumulated in the soldering parts of the BGApackage 5, which is soldered to the printed circuit board on the backside of the navigation key. As a result, peeling-off of the solderingpart will highly possibly occur.

[0005] The soldering parts are located on the back side of the BGApackage 5. Therefore, when the soldering part is peeled off, it isdifficult to repair the peeled soldering part by re-soldering.Accordingly, the whole printed circuit board 4 must be replaced with anew one. This creates a problem of increasing the repairing cost. Such alow reliability of the soldering parts results in low reliability of theportable telephone set. The same problem arises in general portableelectronic devices which each allow the user to play a game, as well asthe portable telephone set.

DISCLOSURE OF THE INVENTION

[0006] Accordingly, an object of the present invention is to provide aportable electronic device and a BGA package protecting device in whicheven when the push buttons are frequently depressed, the soldering partsof the BGA packages mounted on the back side of the operation button canbe maintained in good conditions.

[0007] According to a first aspect of the invention, there is provided aportable electronic device in which microswitches controlled byoperation buttons are mounted on one side of a printed circuit board,and circuit elements accommodated in BGA packages are soldered on theother side of the printed circuit board, wherein a shield wall forsurrounding the BGA packages is mounted on the printed circuit board,and a protrusion portion for holding down the shield wall on the printedcircuit board is protruded from a case of the portable electronicdevice. With such a construction, even if the operation button isoperated and a deformation force acts on the printed circuit, theprinted circuit board is restricted from being deformed at least withinan area surrounded by the shield wall.

[0008] According to a second aspect of the invention, there is provideda portable electronic device in which microswitches controlled byoperation buttons are mounted on one side of a printed circuit board,and circuit elements accommodated in BGA packages are soldered on theother side of the printed circuit board, wherein protrusion portion forholding down surfaces of the BGA packages on the printed circuit boardis protruded from the case of the portable electronic device. With sucha construction, even if the operation button is operated and adeformation force acts on the printed circuit, the BGA packages arepressed by the printed circuit board, so that the soldering parts aremaintained in good conditions.

[0009] According to a third aspect of the invention, there is provided aportable electronic device in which microswitches controlled byoperation buttons are mounted on one side of a printed circuit board,and circuit elements accommodated in BGA packages are soldered on theother side of the printed circuit board, wherein a shield wall forsurrounding the BGA packages is mounted on the printed circuit board, afirst protrusion portion for holding down the shield wall on the printedcircuit board is protruded from a case of the portable electronicdevice, and second protrusion portion for holding down surfaces of theBGA packages on the printed circuit board is protruded from the case ofthe portable electronic device. With such a construction, a protectingeffect of protecting the soldering parts by the first protrusion portionand a protecting effect of protecting the soldering parts by the secondprotrusion portion synergistically act to thereby secure a furtherprotection of the BGA packages.

[0010] According to a fourth aspect of the invention, there is provideda BGA package protecting device for protecting soldering parts of a BGApackage soldered on a printed circuit board, wherein a shield wall forsurrounding the BGA packages is mounted on the printed circuit board,and a member for holding down the shield wall on the printed circuitboard along the shield wall is provided. With such a construction, evenif a deformation force acts on the printed circuit, the printed circuitboard is restricted from being deformed at least within an areasurrounded by the shield wall. As a result, stress applied to thesoldering parts of the BGA packages is lessened.

[0011] According to a fifth aspect of the invention, there is provided aBGA package protecting device for protecting soldering parts of a BGApackage soldered on a printed circuit board, wherein a shield wall forsurrounding the BGA packages is mounted on the printed circuit board, acase of the portable electronic device includes a first member forholding down the shield wall on the printed circuit board and secondmembers for holding down surfaces of the BGA packages on the printedcircuit board. With such a construction, a protecting effect ofprotecting the soldering parts by the first member and a protectingeffect of protecting the soldering parts by the second membersynergistically act to thereby secure a further protection of the BGApackages.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a rear view showing a portable telephone set accordingto a first embodiment of the present invention.

[0013]FIG. 2 is a transverse cross sectional view showing the portabletelephone set according to the first embodiment of the invention.

[0014]FIG. 3 is a transverse cross sectional view showing a portabletelephone set according to a second embodiment of the invention.

[0015]FIG. 4 is a model diagram, when viewed from top, showing a BGApackage potion of the portable telephone set according to the secondembodiment of the invention.

[0016]FIG. 5(a) is a model diagram, when viewed from top, showing a BGApackage portion of a portable telephone set according to a firstmodification of the second embodiment of the invention, and FIG. 5(b) isa cross sectional view showing a key portion of the portable telephoneset according to the first modification of the second embodiment of theinvention.

[0017]FIG. 6(a) is a model diagram, when viewed from top, showing a BGApackage portion of a portable telephone set according to a secondmodification of the second embodiment of the invention, and FIG. 6(b) across sectional view showing a key portion of the portable telephone setaccording to the second modification of the second embodiment of theinvention.

[0018]FIG. 7 is a transverse cross sectional view showing a portabletelephone set according to a third embodiment of the invention.

[0019]FIG. 8 is a rear view showing a conventional portable telephoneset.

[0020]FIG. 9 is a transverse cross sectional view showing theconventional portable telephone set.

[0021] In the figure, reference numeral 10 is a portable telephone set10; 11 is a push button; 12 is a microswitch; 13 is a printed circuitboard; 14, 15 and 16 are BGA packages; 17 is a front case; 18 is a rearcase; 18 b is a protrusion portion for holding down a shield wall; 18 c,18 d and 18 e are bosses (projections); 21 is a shield plate; 22 is ashield wall; and 23 is a shield cover.

BEST MODE FOR CARRYING OUT THE INVENTION

[0022] Embodiments of the present invention will be described withreference to the accompanying drawings.

[0023]FIG. 1 is a rear view showing a portable telephone set accordingto a first embodiment of the present invention. FIG. 2 is a crosssectional view taken on line II-II in FIG. 1. In a portable telephoneset 10 constructed according to the present invention, BGA packages 14,15 and 16 are soldered to a back side of a printed circuit board 13which has microswitches 12 mounted on the front side thereof, which areeach turned on when a push button 11 associated therewith is depressedand turned off when the user's finger is detached from the button.

[0024] An outer peripheral part of the printed circuit board 13 is heldbetween a rib 17 a protruded from a front case 17 of the portabletelephone set 10 and a rib 18 a protruded from a rear case 18 of theportable telephone set 10. A battery housing portion 19 is formed in theback side of the rear case 18, and covered with a back cover 20.

[0025] The portable telephone set 10 of the embodiment is arranged suchthat the integrated circuits including those of the BGA package, whichare mounted on a printed circuit board 13, are soldered collectively toone location and their are covered with a shield plate 21.

[0026] The shield plate 21 is formed with a stainless plate, forexample. The shield plate includes a shield wall 22 for surroundingcollectively the BGA packages 14, 15 and 16 standing upright on theprinted circuit board 13 and a shield cover 23 which is fit to an outerperipheral end of the shield wall 22, and covers an upper surfaceopening part surroundingly defined by the shield wall 22. The lower endof the shield wall 22 is fixed to the printed circuit board 13 bysoldering or another suitable fixing means, and heat radiation holes areformed at proper positions of the shield cover 23.

[0027] Thus, the shield wall 22 for surrounding the BGA packages 14, 15and 16 is provided in the embodiment. Even when a force of depressingthe push button 11 is applied to the printed circuit board 13, thedepressing force is weak and fails to deform the shield wall 22 in adirection horizontal to the wall surface of the shield wall 22 and hencefails to give stress to the soldering parts of the BGA packages 14, 15and 16. Thus, the shield wall 22 functions as a protecting device forthe BGA packages 14, 15 and 16.

[0028] The instant embodiment further includes a BGA package protectingdevice for restricting a deformation of the printed circuit board 13, inaddition to the shield wall 22. The BGA package protecting device isformed with a rib-like protrusion portion 18 b protruded from the rearcase 18 of the portable telephone set 10, and the protrusion portion 18b holds down the shield cover 23 on the shield wall 22. The protrusionportion 18 b may be formed continuously or discretely over the entirecircumference of the shield wall 22.

[0029] Use of such a structure that the shield wall 22 is pressed downwith the rear case 18 further restricts a deformation of the printedcircuit board 13 surrounded by and within the shield wall 22. And, muchless stress is imparted to the soldering parts of the BGA packages 14,15 and 16, which are surrounded by and located within the shield wall22. Therefore, even when the push buttons 11 are frequently depressed inplaying a game, there is less chance that the BGA packages 14, 15 and 16are peeled off, and a reliability of the portable telephone set isfurther enhanced.

[0030]FIG. 3 is a cross sectional view showing a portable telephone setaccording to a second embodiment of the invention. The second embodimentemploys protecting bosses (protrusion portion) 18 c protruded from therear case 18 instead of the protecting boss 18 b of the rear case 18,which is employed in the first embodiment shown in FIG. 2, and thoseprotecting bosses press down the BGA packages 14, 15 and 16 against theprinted circuit board 13. FIG. 4 show the shape and positions of theprotecting bosses 18 c when the bosses press down the surfaces of theBGA packages 14, 15 and 16.

[0031] Boss insertion holes 23 a are formed at positions of the shieldcover 23, which correspond respectively to the central parts of the BGApackages 14, 15 and 16. The protecting bosses 18 c extend from the rearcase 18, pass through the boss insertion holes 23 a and reach thesurfaces of the BGA packages 14, 15 and 16. Preferably, the tip of eachof the protecting bosses 18 c is brought into close contact with thesurface of each of the BGA packages 14, 15 and 16. Actually, however, aslight gap is present between them as shown in FIG. 3 since productiontolerances of the related component parts are present.

[0032] Even when the gap is present, the gap is small, about 0.1 mm.Therefore, even if the printed circuit board 13 is deformed a distanceclose in value to the soldering part by the depressing force to the pushbutton 11, the peeling-off of the soldering part does not occur. Therear case 18 restricts a further deformation of the printed circuitboard 13 which exceeds the gap. Consequently, the soldering part can bemaintained in good conditions with lapse of time.

[0033] FIGS. 5(a) and 5(b) and FIGS. 6(a) and 6(b) are explanatorydiagrams for explaining embodiments of the invention in which shapes ofthe protecting bosses are each changed from that of the alreadydescribed one. The protecting bosses hold down the BGA packages at widerareas, so that the holding effect of the BGA packages is increased. Thesize increase of the protecting bosses possibly hinders heat radiationof the BGA packages, and increases material cost and the weight of theportable telephone set.

[0034] To cop with this, in the embodiment shown in FIGS. 5(a) and 5(b),the surfaces of the BGA packages 14, 15 and 16 are held down withprotecting bosses 18 d each shaped like a cross. In the embodiment shownin FIGS. 6(a) and 6(b), the surfaces of the BGA packages 14, 15 and 16are held down with protecting bosses 18 e each shaped like a rectangle.Since the protecting bosses are cross or rectangle shaped, theprotecting bosses do not hinder the heat radiation of the BGA packages.

[0035]FIG. 7 is a cross sectional view showing a portable telephone setaccording to a third embodiment of the invention. The instant embodimentis featured substantially by a combination of the feature of the firstembodiment (the protrusion portion 18 b formed along the shield wall 22shown in FIG. 2) and the feature of the second embodiment (theprotecting bosses 18 c shown in FIG. 3). It is evident that theprotecting bosses 18 d and 18 e shown in FIGS. 5 and 6 may be used forthe protecting bosses.

[0036] Since the third embodiment has both the features of the first andsecond embodiments, those features synergistically act to more lessenthe stress applied to the soldering parts of the BGA packages 14, 15 and16. Therefore, even when the push button 11 is repeatedly and frequentlydepressed, the soldering parts can be maintained in good conditions fora long period of time.

[0037] While the invention has been described in detail and usingspecific embodiments, it will be apparent to those skilled in the artthat various changes, alteration, modification and variations may bemade without departing from the spirit and scope of the invention.

[0038] This application is based on Japanese Patent Application No.2001-279871, filed Sep. 14, 2001, the contents of which are incorporatedherein by reference.

INDUSTRIAL APPLICABILITY

[0039] As seen from the foregoing description, in the invention, evenwhen the operation buttons are frequently operated, the soldering partsof the BGA packages mounted on the back side of the operation button canbe maintained in good conditions. As a result, a reliability of theportable electronic device is improved.

1. A portable electronic device in which microswitches controlled byoperation buttons are mounted on one side of a printed circuit board,and circuit elements accommodated in BGA packages are soldered on theother side of said printed circuit board, said portable electronicdevice is characterized in that: a shield wall for surrounding said BGApackages is mounted on said printed circuit board, and a protrusionportion for holding down said shield wall on said printed circuit boardis protruded from a case of said portable electronic device.
 2. Aportable electronic device in which microswitches controlled byoperation buttons are mounted on one side of a printed circuit board,and circuit elements accommodated in BGA packages are soldered on theother side of said printed circuit board, said portable electronicdevice is characterized in that: a protrusion portion for holding downsurfaces of said BGA packages on said printed circuit board is protrudedfrom said case of said portable electronic device.
 3. A portableelectronic device in which microswitches controlled by operation buttonsare mounted on one side of a printed circuit board, and circuit elementsaccommodated in BGA packages are soldered on the other side of saidprinted circuit board, said portable electronic device is characterizedin that: a shield wall for surrounding said BGA packages is mounted onsaid printed circuit board; a first protrusion portion for holding downsaid shield wall on said printed circuit board is protruded from a caseof said portable electronic device; and a second protrusion portion forholding down surfaces of said BGA packages on said printed circuit boardis protruded from said case of said portable electronic device.
 4. A BGApackage protecting device for protecting soldering parts of a BGApackage soldered on a printed circuit board, said BGA package protectingdevice is characterized in that: a shield wall for surrounding said BGApackages is mounted on said printed circuit board; and a member forholding down said shield wall on said printed circuit board along saidshield wall is provided.
 5. A BGA package protecting device forprotecting soldering parts of a BGA package soldered on a printedcircuit board, said BGA package protecting device is characterized inthat: a shield wall for surrounding said BGA packages is mounted on saidprinted circuit board; and a case of said portable electronic deviceincludes a first member for holding down said shield wall on saidprinted circuit board and second members for holding down surfaces ofsaid BGA packages on said printed circuit board.